1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display, and more particularly, to a method for manufacturing a liquid crystal display comprising a liquid crystal mixture having a high melting point.
2. Description of the Prior Art
With progression of large-sized liquid crystal displays (LCDs), a requirement for wider viewing angle is confronted. Therefore the multi-domain vertical alignment (MVA) LCD, which possesses advantages such as wider viewing angle and shorter response time, has become a mainstream of the large-sized LCDs. To save time of dropping liquid crystal molecules, most of the large-sized LCDs use a new method, which is called one drop fill (ODF) process, to fill the space between a top substrate and a bottom substrate with liquid crystal molecules. The one drop fill process coats a sealant on the surface of glass substrate. Then, the liquid crystal molecules are directly dropped on the glass substrate. Next, the combination of the top and bottom glass substrate is performed to cure the sealant by the curing process, such as lighting or heating, so as to fix the top and bottom glass substrates together. The manufacture of the LCD is finished. This kind of new process can largely save the time of dropping the liquid crystal molecules and the quantity of the liquid crystal materials, especially for the extra large-sized display.
In a conventional MVA LCD, a protrusion is utilized to make the liquid crystal molecules have a pre-tilt angle. Therefore processes such as thin film deposition, photolithography process, and etching process are needed to form the protrusion, and thus complexity and cost of the fabrication are increased. More serious, the protrusion shades light, reduces aperture ratio of the pixel, and reduces brightness of the LCD. Therefore, the ordinary skilled person in the art provides a polymer stability alignment (PSA) process, also called phase separation alignment (PSA) process, to replace the protrusion so as to make the molecules have pre-tilt angle in the MVA LCD.
Generally, a liquid crystal mixture comprising the liquid crystal molecules and a reactive monomer is provided in the LCD during the polymer stability alignment process. After combining the top and bottom substrate of the LCD, a voltage is applied to tilt the liquid crystal molecules to a predetermined angle. Then, an ultraviolet (UV) light is provided to illuminate the LCD, so that polymerization and phase separation of the reactive monomer in the liquid crystal mixture is gradually caused along the aligned direction of the liquid crystal molecules to form polymers. Therefore, the liquid crystal molecules have a pre-tilt angle along the aligned direction of the liquid crystal molecules.
However, as the aforementioned, after finishing the combination of the top and bottom glass substrate and the filling of the liquid crystal mixture, the LCD also needs to undergo a curing process to cure the sealant between the top and bottom glass substrate. The UV light or the thermal energy applied during the sealant-curing process usually makes the reactive monomer have a phenomenon of deterioration or reaction before the polymer stability alignment process. Therefore, during the following polymer stability alignment process, the polymerization and the phase separation of the reactive monomer cannot be effectively caused to make the liquid crystal molecules have pre-tilt angle. Thus, the composition and the stability of the liquid crystal mixture are also affected, and some mura are further generated in the LCD, such as little bright point generated in displaying image.
According to the aforementioned, the research in the current technology has to be continued so as to provide a better method for manufacturing the LCD and effectively prevent from affecting the quality of the LCD resulted from the deterioration of the reactive monomer before the polymer stability alignment process in the prior art.